1. Field
Although not so limited in its utility or scope, implementations of the present invention are particularly well suited for the fabrication of variously configured optical fiber components including optical fiber tapers.
2. Brief Description of Illustrative Environments and Related Art
Manufacturers of optical fiber components encounter circumstances in which the outer or “peripheral” geometry of a single light-conductive element, or a unitary bundle of the same, must be one that does not generally result conveniently from the well-known heating and drawing process. In addition, some applications require the formation of what are known in the industry as a “tapers.” A taper, as the name implies, is a light-conductive component the cross-sectional area of which increases or decreases as a function of displacement along the longitudinal axis of the component. Traditional methods of achieving an irregular or varying peripheral geometry include (i) heating glass within a mold of desired shape, (ii) molding a form from glass “gobs” and, for the formation of tapers, (iii) heating and stretching a central portion of a glass component in order to form a region of gradually decreasing cross-sectional area. Although difficulties are encountered in connection with the formation of optical fiber components having special cross-sectional configurations of constant cross-sectional area, even more challenging is the formation of tapered components generally and, more particularly, tapered components exhibiting unusual cross-sectional geometries (e.g., other than round or square).
Designers and fabricators of optical fiber components are familiar with variously configured optical fiber “tapers” formed for alternative applications including, for example, (i) use as image reducers/enlargers and (ii) the alteration of numerical aperture along an optical path. For the former application, a taper typically includes a plurality of internally-reflecting light conduits (e.g., light-conductive fibers), each of which conduits conducts a portion (e.g. a “pixel”) of an image introduced into one end of the taper for communication to the opposite end where the numerous pixels combine to form either a reduced or enlarged image. A taper of the type used to alter numerical aperture typically includes opposed incident and emission ends, an optical core extending between the incident and emission ends and an optical cladding disposed about the core, wherein the core and cladding exhibit relative refractive indices that facilitate light propagation by total internal reflection between the incident and emission ends. Depending on whether the numerical-aperture alteration taper is implemented to reduced or increase the numerical aperture along the optical path into which it is situated, the taper is oriented such that the small end (i.e., the end of smaller cross-sectional geometry) serves as one of the incident and emission ends and the large end serves as the other of the incident and emission ends. As is known to those in the field, the opposed small and large ends exhibit, respectively, a small-end numerical aperture and a large-end numerical aperture lower in magnitude than the small-end numerical aperture.
An illustrative traditional method of fabricating a numerical-aperture alteration taper begins with the creation of a basic internally-reflecting light conduit comprising a cladding material collapsed about a core material and exhibiting a uniform cross-sectional geometry and area. Known to those of skill in the relevant arts is that such a conduit exhibits a numerical aperture the mathematical expression for which is NA=(n12−n22)1/2 where n1 represents the refractive index of the core material and n2 represents the refractive index of the cladding material. An intermediate portion of the basic light conduit is heated and stretched such that the intermediate portion is gradually constricted and exhibits a diameter and cross-sectional area that varies with position along the length of the conduit within the stretched intermediate portion (i.e., transition region) such that the basic conduit assumes what is referred to in the art as an “hour glass” shape. If the basic conduit is cut at the center of the transition region, for example, two tapered conduits are formed each of which tapered conduits includes a tapered segment and a segment of relatively constant diameter and cross-sectional area. It will be appreciated that, if desired, a taper exhibiting a diameter and a cross-sectional area that vary over its full length may also be cut from the transition region or from the tapered segment of a tapered conduit. As previously explained, a cladded-core taper made in accordance with the aforementioned or some alternative method includes opposed small and large ends. The small end of the taper exhibits a numerical aperture corresponding to the numerical aperture of the basic light conduit from which the taper was formed, a phenomenon that is generally true regardless of from where along the transition region the small end was cut. However, the larger end exhibits a different numerical aperture that is lower in magnitude than the numerical aperture of the small end of the taper. The value of the numerical aperture at the large end is equal to the inverse of the magnification ratio of the taper multiplied by the numerical aperture of the basic light conduit from which the taper was formed. Accordingly, in going from the small end to the large end, the magnitude of the numerical aperture of the taper is reduced. Among the disadvantages of a taper fabrication method such as that described above are the facts that the process is (i) time consuming and (ii) difficult to replicate precisely over multiple components, thereby frequently resulting in unacceptable variations in dimensional precision among components fabricated pursuant to the same specification requirements.
For some applications, specially-configured optical components can be formed from a molded translucent polymeric material (e.g., plastic), thereby obviating many of the physical difficulties of working with glass. However, when exposed to ultraviolet light and intense heat over sustained periods of time, plastics breakdown and eventually fail. Consequently, polymeric optical components have proven ill-suited for applications in which they are placed in close proximity to intense heat and ultraviolet sources.
Accordingly, there is a need for specially shaped light conduits that are more convenient to precisely and consistently form than glass conduits, but that exhibit the durability of glass when exposed to ultraviolet light.